The administration of therapeutically active peptides and proteins has generally been limited to injection due to difficulties in achieving the required bioavailability via alternative, less invasive routes such as oral, transmucosal, or transdermal. For instance, administration by ingestion can result in chemical and enzymatic degradation in the gastrointestinal tract, resulting in a substantial loss of activity and low bioavailability. Transmucosal delivery through absorptive mucous membranes such as oral, buccal, sublingual, eye, nasal, pulmonary, rectal, and vaginal membranes, on the other hand, has the advantage of being noninvasive and of bypassing hepato/gastrointestinal clearance (at least initially). Peptides and proteins, however, are generally not well absorbed through mucosae because of their molecular size and hydrophilicity. In general, enzyme inhibitors and absorption enhancers need to be coadministered for successful transmucousal delivery of bioactive peptides and proteins.
Classes of absorption enhancers used for transmucosal delivery include bile salts and their derivatives, taurodihydrofusidates, mono- and polycarboxylic acids, cyclodextrins, surfactants (especially non-ionic), chelating agents, cationic polymers, lipids and phospholipids (see Davis and Illum, Clin Pharmacokinet., 42:1107-1128, 2003 for a review). Each of these agents exerts its enhancing effects by a different mechanism, and many have been associated with various degrees of adverse effects. Nonetheless, these enhancers have been demonstrated to enhance the absorption and, consequently, bioavailability of peptides and proteins across the mucous membrane.
The nasal cavity provides an attractive route for peptide and protein delivery because of its relatively high permeability and ease of administration. Nasal spray compositions containing a chelating agent such as disodium ethylenediaminetetraacetate, or bile salt have been shown to enhance the absorption of nona- and deca-peptides having LHRH agonist or antagonist activity (U.S. Pat. Nos. 4,476,116 and 5,116,817). A combination of bile salt and dimethyl-β-cyclodextrin has been used to enhance the nasal absorption of parathyroid hormones (U.S. Pat. No. 5,977,070). Lysophospholipids, acylcamitines and polyoxyethylene(20) sorbitan monooleate (Tween® 80) have also been used as enhancers for the delivery of insulin and calcitonin across mucous membranes (U.S. Pat. Nos. 5,804,212 and 6,440,392). The cationic polysaccharide chitosan, used as powder, nanoparticle, or in solution, has been demonstrated to enhance mucosal absorption of insulin, other peptides and proteins, and vaccines (U.S. Pat. No. 6,391,318; Dyer et al., Pharm. Res., 19:998-1008, 2002; Illum et al., Pharm. Res., 11:1186-1189, 1994; Fernandez-Urrusuno et al., Pharm. Res., 16:1576-1581, 1999). Additionally, bioadhesive agents, such as carbomers and polycarbophil, have been used to increase the residence time and therefore the bioavailability of insulin from a powder dosage form (Callen and Remon, Controlled Rel., 66:215-220, 2000).
The cationic polyamino acid, polylysine, was mentioned in an aerosol formulation for pulmonary and nasal delivery, but no rationale for its function was given (U.S. Pat. No. 6,294,153). Another cationic polyamino acid, poly-L-arginine was reported to enhance the absorption of fluorescein isothiocyanate labeled dextran (Nasume et al., Intl. J. Pharm., 185:1-12, 1999), but no bioactive peptides or proteins were investigated. Other applications for potential uses of cationic polyamino acids to improve transmucosal delivery of molecules can be found in U.S. Pat. Nos. 5,554,388 and 5,788,959; Japanese Patent Applications 1998095738A, 2000281589A; McEwan et al., Biochim. Biophys. Acta, 1148:51-60, 1993; Uchida et al., Exp. Lung Res., 22:85-99, 1996; Natsume et al., Drug Deliv. Systems, 14:21-25, 1999; Miyamoto et al, Intl. J. Pharma., 226:127-138, 2001; Miyamoto et al., Eur. J. Pharma Biopharma., 52:21-30, 2001; Ohtake et al., J. Controlled Res., 82:263-275, 2002 and Ohtake et al., Pharm. Res., 20:1838-1845, 2003. Many of these papers describe the use of cationic polyamino acids to deliver marker molecules such a labeled dextran rather than proteins or peptides. Thus, there remains a need for improved absorption enhancers for use in the transmucosal delivery of bioactive peptides and proteins.